The chromosomal translocation (15;17) which produced the PML-RAR alpha fusion gene had been found in acute promyelocytic leukemia (APL) cells. It was identified that the RAR alpha gene on chromosome 17 and PML gene on chromosome 15 were involved in this translocation. For study the molecular mechnisms of t(15:17) in APL, we cloned and sequenced the junctional region of the chromosomal reciprocal translocation in one APL patient. Furthermore, we compared 21 junctional sequences which had been reported with the consensus sequence of the DNA-topoisomerase I-binding sites...